This invention relates to a structure for mounting a semiconductor device for driving a liquid crystal display device on a substrate of the liquid crystal display device for electrical and mechanical connection therebetween, and the semiconductor device for implementing such a structure, particularly, to a surface-mounting type semiconductor device provided with bumps (protruded electrodes) for electrical connection with the liquid crystal display device.
Surface-mounting type semiconductor devices have come into widespread use as a semiconductor device making up an integrated circuit (IC), a large scale integrated circuit (LSI), and so forth.
Among the surface-mounting type semiconductor devices, there is one type provided with a multitude of bumps placed in lines on the upper surface thereof for electrical and mechanical connection with a wiring pattern on a circuit board when mounting the same on the circuit board. FIG. 15 shows the cross-sectional construction of a semiconductor device provided with bumps formed in a straight-wall shape by way of example.
With this semiconductor device, a multitude of electrode pads 74 for connection with an external circuit are provided along side edges of a semiconductor chip 72, running in a direction orthogonal to the plane of the figure, on the surface (the upper face in the figure) of the semiconductor chip 72 with an integrated circuit (not shown) formed thereon. In FIG. 15, only one of a plurality of the electrode pads 74, 74, disposed in respective lines along the side edge on both sides of the semiconductor chip 72, is shown.
An insulating film 76 having openings formed in such a way as to cover a peripheral region of the respective electrode pads 74, and to mexpose the inside of the respective peripheral regions is provided on the entire upper surface of the semiconductor chip 72, and a lower electrode 79 is provided so as to be in intimate contact with the peripheral region of the respective openings of the insulating film 76, and an exposed part of the respective electrode pads 74. Further, on top of the respective lower electrodes 79, bumps 78 formed in a straight-wall shape are provided.
Thus, the semiconductor device is provided with the bumps 78 formed in a straight-wall shape. In contrast, there is another type of semiconductor device provided with bumps formed in a mushroom shape, wherein the top part of the bumps is larger than the base thereof. However, the semiconductor device provided with the bumps formed in a straight-wall shape is more suitable for reducing lateral spread thereof, along a semiconductor substrate 72, and to that extent, a placement density of the bumps can be rendered higher, so that a connection pitch with the external circuit can be miniaturized.
Such surface-mounting semiconductor devices provided with the bumps as described have come to be used as semiconductor devices for driving a liquid crystal display device, and a plurality of such semiconductor devices for use in driving (scanning and inputting signals) have come to be mounted on a peripheral region of a glass substrate making up a liquid crystal panel of the liquid crystal display device.
Accordingly, a conventional structure for mounting a semiconductor device on such a liquid crystal display device is described hereinafter with reference to FIG. 16 by way of example.
Reference numeral 80 denotes a liquid crystal display device wherein liquid crystal 85 is sealed in-between a first substrate 81 and a second substrate 82, making up a liquid crystal panel, by use of a sealing material 86, and a region 8 of the first substrate 81 where the first substrate 81 is extended beyond an edge of the second substrate 82 is a region where a semiconductor device 71 for driving the liquid crystal display device 80 is mounted. For the first and second substrates 81, 82, respectively, a glass substrate is generally used, however, a transparent resin substrate, or the like may be used as well.
A multitude of scanning electrodes 83 extending to the region 8 from the interior of the liquid crystal display panel with the liquid crystal 85 sealed therein, and a multitude of terminal electrodes 88 serving as connecting terminals to the external circuit are composed of a transparent and electrically conductive film, and are patterned on the upper surface of the first substrate 81 in such a way as to be placed in lines across the direction orthogonal to the plane of the figure. A multitude of signal electrodes 84 are composed of a transparent and electrically conductive film, and are patterned on the inner surface of the second substrate 82, opposite to the scanning electrodes 83 across the liquid crystal 85, in such a way as to be placed in lines across the transverse direction in the figure.
An anisotropic conductive adhesive 50 composed of electrically conductive particles 52 dispersed in an insulating adhesive is applied onto the region 8 of the first substrate 81 of the liquid crystal display panel 80. Then, the semiconductor device 71 in a posture inverted from that shown in FIG. 15 is disposed on the region 8 of the first substrate 81 after alignment of the respective bumps 78 with the respective scanning electrodes 83 and the respective terminal electrodes 88 that are to be connected with the respective bumps 78.
With the semiconductor device 71 being set on the first substrate 81 with the anisotropic conductive adhesive 50 applied thereon as described above, pressure is applied to the semiconductor device 71 against the first substrate 81, and at the same time, heat treatment is applied thereto, thereby electrically connecting the respective bumps 78 with the respective scanning electrodes 83 and the respective terminal electrodes 88 through the intermediary of the electrically conductive particles 52 contained in the anisotropic conductive adhesive 50. Concurrently, the semiconductor device 71 is bonded to, and securely mounted on the first substrate 81 by the insulating adhesive contained in the anisotropic conductive adhesive 50.
Further, an end of a flexible printed circuit board (FPC) 60 is disposed on a part of the upper surface of the first substrate 81 where the terminal electrodes 88 are formed. A wiring pattern (not shown) composed of a copper foil, for providing the semiconductor device 71 with a power supply source and input signals, is formed on the FPC 60.
The wiring pattern is also electrically connected with the respective terminal electrodes 88 on the first substrate 81 through the intermediary of the electrically conductive particles 52 contained in the anisotropic conductive adhesive 50, and at the same time, the end of the FPC 60 is bonded to, and securely mounted on the first substrate 81.
By mounting the semiconductor device 71 in the manner as described above, the electrically conductive particles 52 contained in the anisotropic conductive adhesive 50 are securely held between the respective bumps 78 and the respective scanning electrodes 83 on the first substrate 81 as well as between the wiring pattern on the FPC 60 and the respective terminal electrodes 88 on the first substrate 81, thereby attaining electrical connection, respectively, and also attaining mechanical connection therebetween, respectively, by the insulating adhesive.
Thereafter, a mold resin 62 is applied to the upper surface of junctions for both the semiconductor device 71 and the FPC 60, as well as peripheral regions thereof. This can prevent moisture from ingressing into junctions between the respective bumps 78 and the respective scanning electrodes 83 as well as junctions between the FPC 60 and the respective terminal electrodes 88 while providing these junctions with mechanical protection, so that reliability of the structure for mounting the semiconductor device can be enhanced.
However, a problem has been encountered with such a conventional structure of mounting the semiconductor device on a liquid crystal display device, that is, an area occupied by those junctions (the region 8 shown in FIG. 16) requires a fairly large size, thus interfering with an aim of downsizing the liquid crystal display device.
For example, the region 8 representing a junction area for joining both the semiconductor device 71 and the FPCs 60 with the liquid crystal display device 80 was found to be about 5 mm in width since it was necessary to take into account 2 mm as a width of the semiconductor device 71, 1 mm as connection allowance for the semiconductor device 71, and 2 mm as connection allowance for the FPC 60.
The region 8 of the liquid crystal display device 80, in which the semiconductor device is mounted, represents non-display sections of the liquid crystal panel, so that a module size of the liquid crystal panel has come to represent a fairly large proportion relative to a display section area.
The invention has been developed to solve the problem described above, and it is therefore an object of the invention to realize downsizing of a liquid crystal display device by reducing an area of a part of the liquid crystal display device, for mounting a semiconductor device on a circuit board thereof, including a part of the liquid crystal display device, for connecting a flexible printed circuit board to the semiconductor device. To this end, the invention provides a structure for mounting a semiconductor device on a liquid crystal display device, and the semiconductor device for implementing the structure.
More specifically, with a structure for mounting a semiconductor device on a liquid crystal display device according to the invention, the semiconductor device provided with bumps electrically conductive with electrode pads formed on a semiconductor chip with an integrated circuit formed thereon, respectively, through the intermediary of respective lower electrodes, formed so as to stretch over both the surface (upper surface) and a sidewall face of the semiconductor chip, is mounted on the liquid crystal display device comprising a first substrate provided with scanning electrodes formed thereon, a second substrate provided with signal electrodes formed thereon opposite to the scanning electrodes, and liquid crystal sealed therein-between. Further, the semiconductor device is mounted on the surface of a part of either of the first substrate and the second substrate, where one of the substrates is extended beyond an edge of the other substrate, such that one sidewall face of the semiconductor chip is opposite the surface, so that the bumps disposed on the side are connected to the electrodes formed on one of the substrates, respectively.
The bumps of the semiconductor device are preferably provided so as to stretch over both the surface (upper surface) and a second sidewall face of the semiconductor chip opposite from a first sidewall face thereof as well as both the upper surface and the first sidewall face, and the semiconductor device is preferably mounted on the surface of the part of either of the first substrate and the second substrate, where one of the substrates is extended beyond the edge of the other substrate, such that the first sidewall face of the semiconductor chip is opposite the surface, so that the bumps stretching over the first sidewall face are connected to the electrodes formed on said one of the substrates, respectively, while a flexible printed circuit board is connected to the second sidewall face of the semiconductor chip, so that a wiring pattern (printed wiring) of the flexible printed circuit board is rendered electrically conductive with the bumps stretching over the second sidewall face.
Otherwise, the bumps of the semiconductor device may be provided so as to stretch over both the surface (upper surface) and a third sidewall face of the semiconductor chip orthogonal to a first sidewall face thereof as well as both the upper surface and the first sidewall face, and the semiconductor device is mounted on the surface of the part of either of the first substrate and the second substrate, where one of the substrates is extended beyond the edge of the other substrate, such that the first sidewall face of the semiconductor chip is opposite the surface, so that the bumps stretching over the first sidewall face are connected to the electrodes formed on said one of the substrates, respectively, while a flexible printed circuit board is connected to the third sidewall face of the semiconductor chip, so that a wiring pattern (printed wiring) of the flexible printed circuit board is rendered electrically conductive with the bumps stretching over the third sidewall face.
Further, a semiconductor device according to the invention is a semiconductor device to be mounted on the liquid crystal display device comprising a first substrate provided with scanning electrodes formed thereon, a second substrate provided with signal electrodes formed thereon, opposite to the scanning electrodes, and liquid crystal sealed therein-between, for driving the liquid crystal display device, comprising: a semiconductor chip provided with an integrated circuit formed thereon with a plurality of electrode pads for connecting the integrated circuit to an external circuit, disposed in the vicinity of side edges of the upper surface thereof; an insulating film formed on the semiconductor chip, having an opening for exposing the respective electrode pads; a lower electrode provided on the respective electrode pads; and a plurality of bumps, each electrically conductive with the respective electrode pads through the intermediary of the respective lower electrodes, provided so as to stretch over both the surface (upper surface) and respective sidewall faces of the semiconductor chip.
The sidewall faces of the semiconductor chip, along which the bumps are provided, respectively, are preferably formed in a setback shape with a difference in level, provided on the side of the surface (upper surface) of the semiconductor chip.
Further, it is desirable that the bumps are provided so as to protrude sideways from the respective sidewall faces of the semiconductor chip. In the case where the sidewall faces of the semiconductor chip are formed in the setback shape with the difference in level, the bumps are preferably provided so as to protrude sideways from the outermost face of the respective sidewall faces.
Further, the bumps are preferably composed of a plurality of metallic layers composed of, for example, a copper layer and a gold layer, or a copper layer, a nickel layer, and a gold layer, deposited in this order from the lower electrode side.